Current-regulating apparatus



M. MORRISON CURRENT REGULATING APPARATUS Oct. 26,. 1926.

Filed Nbv', 15, 1921 ATTORNEY i7 Patented Oct. 26, 1926. g I

UNITED STATES PATENT- QFFICE.

MONTFORD 1!IORRI $0N,.0F. NEW YORK, N. Y.

CURRENT-REGULATING APPARATUS.

Application filed November 15, 1921. Serial No. 515,228. I

This invention relates to electrical control apparatus and more particularly to means for automatically maintaining an electrical current constant.

The necessity of maintaining an electrical current constant inorder to secure the most efiicient operation of many types of electrical apparatus is well known. An X-ray tube may be mentioned as an example of an electrical device which should be operated with a steady current on account of the desirability of maintaining constant a desired volume of X-rays.

It is, therefore, an object of the invention to provide means for automatically limiting the current in an electrical circuit.

A special object of the invention is the provision of means for maintaining the discharge current in a hot cathode X-ray de vice constant independent of the specific emissivity of the cathode and of the line voltage variation.

Other objects will be appreciated uponv reading the following specification.

Constant current regulators of the prior art have consisted for the most part of moving elements which are admitted to be objectionable. v I

The present invention provides a constant current regulator orstabilizer which has no moving members and whichoperates' on purely electrical phenomena.

According to my invention, the current in an electrical circuit iscontrolled by regulating the magnitude of an electron stream existing in a vacuum and exerting an influence on the current in the main circuit.

This electron stream may be partially or wholly cut out by deflecting it from the normal path by means of a magnetic field. If the strength of the magnetic field is made a function of the current in the main circuit to be controlled, the deflection of the electron panying stream will vary with the main current, but in an opposite sense, and, since it exerts a control over the main current, the latter will thus be automatically controlled.

My invention will be more clearly understood by reference to the following description taken in connection with the accomdrawing which is a diagrammatic representation of an embodiment of my new stabilizer, showing its application to an electron discharge device, such as an X-ray tube, for the purpose of maintaining the current constant.

Referring to the drawing, the high tens1on secondary coil 5 of a transformer 7, having C011 9 as the primary, is connected by means of conductor 10 to a terminal 11 of an X-ray tube 12. The tube 12 comprises an evacuated envelope 1 1, which may be of glass, having oppositely extending arms 15 and 16 into which are sealed, re-

-l1eating circuit of cathode 18 is connected a vacuum electron tube 30' comprising an evacuated envelope 31 containing a cathode of filamentary form consisting of tungsten or other refractory material and adapted to be heated to an electron emitting temperature by reason of having its terminals connected by means of conductors 34 and to the secondary 26 of the transformer 24. Within the envelope 31, concentrically disposed with relation to cathode 32, is a cylindrical plate 38 constituting the anode of the tube 30 and connected by means of conductor 39 to leading-in conductor 20 of the oathode 18. Encircling the cylindrical plate 38,v but insulated therefrom, is a conducting helical coil or solenoid 40 connected at 42 and 44 in parallel with that portion of the main circuit containing a variable reactor 47 to a terminal of the secondary coil 5 of the transformer 7. I

In the normal operation of the circuit, a constant voltage from the secondary coil 26 is applied to filament 32 sufficient to maintain it at a temperature not lower than that 46 which isconnected by means of conductor L variable reactor 28 and serves with the elecformer coil 5, the reactor 46, the helical coil V and thereby controlling the ampere turns and 40 in parallel and the X-ray tube 12. I

The passage of current through coil 40 creates within the cylinder 38 a magnetic field parallel to the axis of the cylinder. In

the presence of this magnetic field, the electrons emanating from the filament 32 travel in curved paths to the plate 38, as contrasted with straight line passage in the absence of a magnetic field. Normally, however, the strength of the field is such that the paths of the electrons intersect the cylinder, that is, the electrons complete their passage from filament 32 to cylinder 38 and thus form part of the heating circuit of cathode 18. V

For adaptation of the stabilizer to various conditions of service, the reactor 46 is made variable for the purpose of influencing the quantity of current passing through coil 40 strength of the magnetic field. In the operation ofthe stabilizing device, the

stren th of the magnetic field is set at sucha v ue that a predetermined increase of current in the main circuit will intensify the magnetic field to the critical strength, that is, the' strength suflicient to prevent the electrons emanating from filament 32 from reaching cylinder 38; by such action the electrons emanating from the hot filament 32 are made to assume curved paths having their origins and terminations 1n filament 32 while the paths do not intersect the cylinder.

It is apparent that thegreater-the number of electrons thus deflected, the less will be the current flow ing through the tube 30 until, when all the electrons emanating from the filament 32 are prevented from reaching the cylinder, an open circuit or practically infinite resistance is efiected. It will be appreciated that the method of thus affecting the electron stream is equivalent to changing the resistance of the circuit so that a greater --or less current is allowed to flow asdesired.

Presuming that it is desired to maintain a steady current in the X-ray tube 12 and that the line voltage applied to transformer 24 fluctuates so as to rise above the normal value, a voltage higher than the normal will be generated 111 the secondary coil 26 from which excess current will flow to the cathode 18 and heat .it to a higher temperature, whereby a greaternumber of electrons are drawn across the vacuous space of tube 12 by a'positive potential on anode 17, constitute a larger electron stream, that is, a larger momentary current through the tube 12. Part of this excess current will pass through the helical-coil 40, thereby creating a stronger magnetic field within cylinder 38.

If the excess current is sufiicient to cause the magnetic field to reach its'critical value the electron stream of tube 30 will be more or less completely deflected, which will be equivalent to the insertion of a greater resistance in the circuit containing tube 30. Since cathode 18 is in the same circuit as tube 30, the former will now receive less heating current than when the normal electron stream is flowing through the tube 30. The lower temperature of cathode 18 resulting from the lower current passing through it will effect the liberation of a smaller'numw ber of electrons. The magnitude of the current passing through tube 12 being dependent upon the number of electrons emanating from cathode 18, it will be seen that the lower temperature of cathode 18 will limit the current passing through tube 12.

Similarly, anexcess voltage generated in transformer coil 5 will raise the magnetic field in tube 30 to the critical degree whereby the electron stream of tube 30 willbe so affected as to result ina lower temperature ofcathode 18 and a diminished electron emisi sion therefrom. and consequently tend to equalize the current through the X-ray tube.

While I haye described indetail one form of stabilizer embodying my invention and circuit arrangement therefor, minor modifications may easily be made in the same, which, however, employ the same underlying principle, and it is desired that it be under;

stood. that such modifications ,come within" thescope of. this invention as embraced in the appended claims.

What is claimed is:

the combination of means for generating an 1. A current stabilizing device comprising electron stream and means responsive to a portion of the current to be stabilized for establishing a variable magnetic field in the path of said stream.

2. In an'electricalcircuit, the combination of a source of ower subject to'variations, means actuated y a portion of the current from the source of power for enerating a magnetic field responsive to sai variations, a vacuum electron tube operating in said magnetic field and regulating the de ree of heating of a cathode of another e ectrori tube. w I

3; In an electrical circuit, the combina-. tion of a source of power subject to variations, means for generating a magnetic field I responsive to said variations, a vacuum electron tube operating in said magnetic field and a hot cathode tube governed by the'electron tube so that the cathode thereof is heated to a greater or less degree inversely as the potential of the source of power varies.

4. An electron discharge apparatus comprising an electron discharge tube, means subject to variations for generating electrons at the cathode of said tube, means for establishing a magnetic field responsive to said variations and means comprising a vacuum electron tube operating in said magnetic field toicompensate for said variations by contrblling the supply of electrons at the cathode.

5. An X-ray apparatus comprising a hot cathode X-ray tube means sub ect to variations for heating t ecathode of said tube and means for controlling the volume of X-rays "generated in said tube, the latter means acting to control the temperature of the cathode of said tube by the action of an electron stream formin part of the cathode circuit-"and governed iy a-magnetic field gelperated by means of current to the X-ray tu e. a

6. An electric discharge system comprising the combination of a hot cathode tube, a heating circuit for the cathodeof said tube, a resistor in said heating circuit, a vacuum electron tube in shunt with said resistor, a power supply circuit for said hot cathode tube and means in said supply circuit for generating a magnetic field within said vacuum electron tube, said magnetic field being responsive to variations of current in said suppl circuit.

7. An e ectric discharge system-comprising the combination of a hot. cathode tube, a heating circuit for the cathode of said tube, a vacuum electrontube in saidheating circuit, a power supply circuit for\ said hot cathode tube and means in said supply circuit for generating ama etic field within said vacuum electron tu e, said ma etic field being responsive to variations 0 .current in sa1d supply circuit.

S 'An electric discharge system comprising the combinationof a hot cathode tube, a heating circuit for the cathode of said tube, a vacuum electron tube in said heating circuit, a power supply circuit for said hot cathode tube, a resistor in said supply circuit and means in shunt with said resistor for generating a magnetic field within said vacuum electron tube.

9. An electric discharge system comprising the combination of a hot cathode tube, a heating circuit for the cathode of said tube, a resistor in said heating circuit, a vacuum electron tube in shunt with said resistor, a power supply circuit for said hot cathode tube, means in said supply circuit for generating a magnetic field within said vacuum electron tube and a resistor in parallel withsaid means.

10. An electric discharge system comprising the combination of a hot cathode tube,

. a heating circuit for the cathode'of said tube, a vacuum electron tube in said heating circuit comprising an evacuated envelope, a cylindrical anode and an incandescent cathode within said anode, a power supply circuit for said hot cathode tube and means in said supply circuit for generating a itiiignetic field within said vacuum electron tu 11'. An electric discharge system comprising the combination of a hot cathode tube, a heating circuit for the cathode of said tube, a vacuum electron tube in said heating circuit comprising an. enclosing evacuated envelope, a cylindrical anode and an incandescent cathode concentricwith said anode, a power supply circuit for said hot cathode tube and means in said supply circuit for generating a magnetic field within said vacuum electron tube and transverse to the flow of electrons therein;

12. An electron dischar e system comprising a hot cathode tube, a heating circuit for the cathode thereof, a stabilizing device comprising an electron tube in said heating circuit, said stabilizing device comprising an anode, an electron-emitting cathode and a solenoid surrounding the same and energized by the power circuit to the hot cathode tube to generate'a magnetic field within the stabilizing device and parallel to the axis thereof. I v

13. In combination, an .electron device, a source of current of variable potential energizing the device and tending to estab lish a var ing electron flow therein, a stabilizing evice comprising an evacuated envelope, an electron-emitting cathode, an anode concentric therewith, a solenoid surrounding both and energized by at least part of the electron flow through the electron device to create a magnetic field substantially transverse to the normal electron flow throu h the stabilizing device to govern said e ectron flow, a current supplied to the cathode of the electron device, at least part of which current passes as electron flow through the stabilizing device and is governed by the magnetic 'field therein, whereby an increased potential of the current supply results in a decreased energizing current for the cathode of the electron device MONTFORD MQRRISON. 

